Breast cancer is one of the most life-threatening tumors among women in U.S. There is considerable evidence that early diagnosis and treatment of breast cancer can significantly increase chances of survival. While X-ray mammography is the current standard screening technique, it is limited by its poor soft tissue differentiation and radiation exposure. Patients with positive mammographic findings require a biopsy for definitive diagnosis, and it was reported that biopsies of breast lesions identified in mammography screenings are negative for malignancy in a significant portion of the patients. We propose to develop a novel, cost-effective, non-ionizing, high resolution, and high specificity imaging system for imaging electrical conductivity by integrating biomagnetism with ultrasound (magnetoacoustic tomography with magnetic induction: MAT-MI) for screening and early detection of breast cancer. This proposed development is based on the experimental evidence that cancerous tissue shows significantly higher electrical conductivity value than normal and benign tissue. In this R21 project, we propose to explore and develop a 3-dimensional (3D) multi-excitation MAT-MI (meMAT-MI) system and evaluate it in computer simulations, phantom experiments, and breast specimen imaging, for the purpose of achieving high resolution, high specificity electrical impedance imaging throughout the volume with a cost effective system realization for breast cancer detection. In the proposed 3D meMAT-MI, the object is located in a static magnetic field and a time-varying pulsed magnetic field. Multiple pulsed magnetic stimulations will be applied to the object, which induce eddy current distributions in the object. Consequently, the sample will emit acoustic waves by the Lorentz force based on the interplay of induced currents and applied magnetic fields. The acoustic signals are collected around the object during multi-excitation to reconstruct images related with the electrical conductivity distribution in the object. Through multi-excitation using magnetic energy, we propose to reconstruct the complete electrical conductivity profiles throughout the volume of the object. We will develop and optimize the novel 3D meMAT-MI system, and assess its feasibility in computer simulations and phantom experiments. We will also test directly its performance in imaging breast tumors in human breast specimens. High resolution imaging of electrical impedance distribution is of significance for a variety of applications in biomedical research and clinical diagnosis, such as early cancer detection. The successful development of a high-resolution, non-ionizing, cost-effective electrical impedance imaging system will have a significant impact to screening and early detection of breast cancer.